This invention relates to spectrometers. The invention has particular but not exclusive application to infra-red spectrometers such as FT-IR spectrometers.
In for example an FT-IR spectrometer infra-red or near infra-red radiation is directed from a source of such radiation towards the sample under investigation. Radiation transmitted by and/or reflected from the sample is received at a detector or receiver and the output of the detector is processed by a signal processor in order to obtain the spectral characteristics of the sample. A typical FT-IR instrument will include an interferometer of the Michelson type for producing a scanning beam which is directed towards the sample to be investigated. Modem spectrometers include powerful signal processors which can carry out Fourier Transform computations on data received from the detector in order to provide spectral data relating to the sample under investigation.
Conventionally in carrying out measurements it is first necessary to obtain a background measurement or measurements, that is to say to measure a background spectrum without a sample in place at the sample station of the instrument. Subsequently measurements are made with the sample in place and the desired sample spectrum is obtained from the ratio of the measurement obtained with the sample in place to the background measurement.
Thus in routine spectrometer operation where the instrument is used to perform identical measurements on either new samples of the same material or samples of similar materials a typical operator sequence will be as follows:
1. prepare sample
2. mount sample either directly or in a sampling accessory
3. perform measurement
4. interpret result.
Each of these operations takes a finite amount of time which affects the apparent response of the instrument.
The present invention is concerned with a spectrometer and a method of operating a spectrometer which is designed to improve that response.
According to one aspect of the present invention there is provided a method of operating a spectrometer which comprises a source of analysing radiation a detector for detecting the analysing radiation and processing means for processing the output of the detector, said method comprising arranging the spectrometer so that it carries out scans on a continuous basis storing spectral data from at least some of the scans, and retrieving an item or items of stored data when carrying out a sample measurement.
The method may comprise the step of inserting a sample into the sample station of the spectrometer and generating under operator control an instruction to initiate a scan.
The method may include the step of associating with the stored data, data indicative of a characteristic of the stored data. The characteristic may be the detected beam energy. The method may comprise arranging the processor so that it recognises automatically the introduction of the sample and carries out a measurement accordingly.
According to another aspect of the present invention there is provided a spectrometer comprising a source of analysing radiation a detector for detecting the analysing radiation and processing means for processing the output of the detector wherein said spectrometer is arranged so that it carries out scans on a continuous basis, and said processor stores spectral data from at least some of the scans and retrieving an item or items of stored data when carrying out a sample measurement.